This invention relates to a detecting device for detecting the revolving speed of a bearing for supporting a wheel of an automobile or the like.
It is essential to detect the revolving speed of the wheels of an automobile with high accuracy on an automobile equipped with an antilock brake system. For this purpose, a pulser ring and a rotation sensor are mounted on a ring of a bearing rotatably supporting each wheel to detect the revolving speed of the wheel by detecting magnetic changes with the rotation of the pulser ring.
It is necessary to provide such a revolving speed detecting device with means for protecting the pulser ring and the rotation sensor against flying stones and muddy water. A device provided with such a protection is disclosed in Japanese Utility Model Application 2-115042 filed by the present applicant.
As shown in FIGS. 7 and 8, this prior device comprises a pulser ring 33 mounted on a rotating ring 31 of a wheel bearing, a ring 34 press-fitted on a fixed ring 32, and a rotation sensor 35 bolted on the outer surface of the press-fitted ring 34. The rotation sensor 35 has a sensing unit 36 received in a hole 37 formed in the ring 34.
A seal member 38 is provided between the press-fit ring 34 and the rotating ring 31 to seal the pulser ring 33 from the surrounding environment.
In the above arrangement, the press-fit ring 34 and the rotation sensor 35 are separate members. This leads to increase in the number of parts to be assembled together. Also, this arrangement requires the provision of a seal member 39 such as an O-ring between the sensing unit 36 and the ring 34 to keep off muddy water or the like.
Further, in order to prevent the rotation sensor 35 from getting loose due to vibration of the car, the torque for tightening the screws with which the sensor 35 is secured to the ring 34 has to be controlled with high accuracy. This lowers the efficiency of assembly work.
Further, in this arrangement, a seal ring 40 is mounted on the ring 34 so as to be in sliding contact with a lip of the seal member 38. This creates the problem of a poor seal between the press-fit ring 34 and the seal ring 40. Also, this arrangement has a problem in that the diametric dimension of the space for accommodating the seal member 38 is small.